Welcome to PC!

I think this is a hard question to answer & perhaps controversial to some. I'll give you my opinion though.

In general I would say that short-term use of APs is not likely to shorten ones life expectancy. What might however, is long term use of APs, particularly at high doses.

How? Well I believe you've hit the nail on the head with regards to two factors that can be a consequence of using APs. Obesity & diabetes. Both are known to shorten life expectancy, particularly diabetes which reduces life expectancy by something like 10 years (for type II). A study by Johns Hopkins also found that high doses of first-generation APs (typical APs) were associated with a greater risk of cardiac disease. (Risperidone is a second-generation, or atypical AP by the way)

However, of interest in that same study it was shown that schizophrenics who adhered to their medication regime, avoided high doses & who regularly saw a mental health professional had a longer life span than they would have off medication. Bear in mind though that's specific to schizophrenics.

So what do we take from this all? The risk in my mind comes from the indirect consequences of some of the side effects of APs. With close monitoring from a doctor you can look out for significant increases in weight or high blood sugar so that if needed medication can be changed. Outwith that you can do your best to eat healthily & regularly exercise.

In your case however I really wouldn't worry. You are only just starting on a low dose of risperidone & you seem quite pro-active, so will know what problems to look out for but as it's a low dose these are unlikely.

As for your diagnosis, I'm interested to know exactly what "early psychosis" refers to. Are you experiencing any hallucinations (hearing or seeing things that aren't there), or have any delusions (strange beliefs or paranoid thinking)? These are usually the things one would associate with psychosis. However I know that typically at a young age like yourself psychiatrists are hesitant to diagnose a specific condition.